Battery cooling system

ABSTRACT

A cordless power tool has a housing which includes a mechanism to couple with a removable battery pack. The battery pack includes one or more battery cells as well as a vent system in the battery pack housing which enables fluid to move through the housing. A mechanism is associated with the battery pack to dissipate heat from the battery pack.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.10/223,908, filed on Aug. 20, 2002, now U.S. Pat. No. 7,014,945, whichis in turn a continuation of U.S. application Ser. No. 09/566,567, filedon May 8, 2000, now U.S. Pat. No. 6,645,666, which is in turn acontinuation-in-part of U.S. application Ser. No. 09/035,586, filed Mar.5, 1998, now U.S. Pat. No. 6,455,186.

BACKGROUND OF THE INVENTION

The present invention relates to battery cooling systems and, morespecifically, to systems for cooling batteries for cordless power tools.

Cordless products which use rechargeable batteries are prevalentthroughout the workplace as well as in the home. From housewares topower tools, rechargeable batteries are used in numerous devices.Ordinarily, nickel-cadium or nickel metal-hydride battery cells are usedin these devices. Since the devices use a plurality of battery cells,the battery cells are ordinarily packaged as battery packs. Thesebattery packs couple with the cordless devices and secure to the device.The battery pack may be removed from the cordless device and charged ina battery charger or charged in the cordless device itself.

As the cordless power device is used, current flows through thebatteries to power the cordless device. As current is drawn off thebatteries, heat is generated within the battery pack. Also, duringcharging of the battery pack, heat is likewise accumulated during thecharging process. The heat created during discharge of the batteries aswell as charging of the batteries which, in turn, leads to increasedtemperatures, may have a severe effect on the life expectancy andperformance of the batteries. In order for batteries to properly charge,the batteries must be below a desired threshold temperature and thedifferential temperature between the cells in the battery pack should beminimized. Likewise, if the batteries become too hot during use, batterylife will be cut short. Also, if a battery is below a certain thresholdtemperature, it will be too cold to charge and must be warmed beforecharging. Thus, it is desirous to maintain batteries within a desiredtemperature range for optimum performance as well as optimum charging.

Further, battery packs typically contain some battery cells close to theouter walls of the pack, while some battery cells are surrounded byother battery cells. Those cells close to the outer walls have betterthermal conductivity to the outside ambient than do the cells that aresurrounded by other cells. When a battery pack is discharging on thecordless device, the amount of heat generated is approximately the samein each cell. However, depending on the thermal path to ambient,different cells will reach different temperatures. Further, for the samereasons, different cells reach different temperatures during thecharging process. Accordingly, if one cell is at an increasedtemperature with respect to the other cells, its charge or dischargeefficiency will be different, and, therefore, it may charge or dischargefaster than the other cells. This will lead to a decline in theperformance of the entire pack.

SUMMARY OF THE INVENTION

The present invention provides the art with a battery pack whichdissipates heat within the battery pack during charging of the cells aswell as discharging of the cells while the battery pack is in use.

Additional objects and advantages of the invention will become apparentfrom the detailed description of the preferred embodiment, and theappended claims and accompanying drawings, or may be learned by practiceof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate an embodiment of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings, the same reference numerals indicate thesame parts.

FIG. 1 is a partial cross-section view of a cordless power tool andbattery in accordance with the present invention.

FIG. 2 is a partial cross-section view of a battery pack in accordancewith the present invention.

FIG. 3 is a cross-section view of another embodiment of a battery packin accordance with the present invention.

FIG. 4A is a cross-section view of another battery pack in accordancewith the present invention.

FIG. 4B is an elevation view of the battery pack of FIG. 4A.

FIG. 4C is a cross-section view of another battery pack in accordancewith the present invention.

FIG. 5 is another cross-section view of a battery pack in accordancewith the present invention.

FIG. 6 is an additional cross-section view of another embodiment of abattery pack in accordance with the present invention.

FIG. 7 is an additional cross-section view of a battery pack inaccordance with the present invention.

FIG. 8 is a cross-section view of an auxiliary fan module in accordancewith the present invention.

FIG. 9 is a perspective view of a charger in accordance with the presentinvention.

FIG. 10 is a cross-section view of the auxiliary fan module coupled withthe charger of FIG. 9 in accordance with the present invention.

FIG. 11 is a cross-section view of another embodiment of the presentinvention of a charger of FIG. 9.

FIG. 12 is a cross-section view like that of FIG. 8 of anotherembodiment of an auxiliary fan in accordance with the present invention.

FIG. 13 is a perspective view of a battery cooler/heater in accordancewith the present invention.

FIG. 14 is a longitudinal cross-section view of FIG. 13.

FIG. 15 is a view like FIG. 14 of an additional embodiment of thebattery cooler/heater.

FIG. 16 is a top plan view of an additional embodiment of a battery packin accordance with the present invention.

FIG. 17 is a front elevational view of the battery pack of FIG. 16.

FIG. 18 is a partial cross-sectional view of the battery pack of FIG. 16along line A-A of FIG. 16 and another embodiment of the charger.

FIG. 19 is a partial cross-sectional view of the battery pack of FIG. 16along line A-A of FIG. 16 and another embodiment of the charger.

FIG. 20 is a front view of the battery pack plenum according to thepresent invention.

FIG. 21 is a front view of the insulation plate according to the presentinvention.

FIG. 22 is an exploded perspective view of components of the batterypack of FIG. 16.

FIG. 23 is a perspective view of the assembled components shown in FIG.22.

FIG. 24 is a side elevational view of another battery pack according tothe present invention.

FIG. 25 is a side elevational view of the opening sealer of the batterypack of FIG. 24.

FIG. 26 is side elevational view of the charger used with the batterypack of FIG. 24.

FIG. 27 is a partial top plan cross-sectional view of the battery packof FIG. 24 along line B-B of FIG. 27 and the charger of FIG. 27.

DETAILED DESCRIPTION

Turning to the figures, a cordless device is illustrated and designatedwith the reference numeral 20. The cordless device ordinarily includes aclamshell type housing 22. The housing 22 includes a mechanism 24 tocouple with a portion of a battery pack 26. The cordless device 20includes electrical elements 28 which couple with the battery packelectrical elements 29. Also, the device includes a trigger 30 whichenergizes the motor 32 within the housing 22.

The battery pack 26 includes a housing 34 which contains a plurality ofbattery cells 36 within the housing 34. Also, the housing 34 includes aventilation system 38 which enables fluid to pass through the housing 34and move around the cells 36 to dissipate heat from the plurality ofcells 36 to the ambient air. The venting system 38 ordinarily includesat least one inlet 40 and at least one outlet 42. The inlet and outletare ordinarily apertures or slots in the housing 34. Also, a channel 44is formed within the housing 26 and aligned with the inlet 40 todistribute the fluid flow around the battery cells 36 so that all of thebattery cells 36 are cooled. Preferably, the fluid flows coaxially withrespect to the axes of the batteries 36. Thus, as fluid enters into thechannel 44, the fluid is directed over the battery cells and does notpass over one cell to the next cell, etc., but is passed over a numberof cells at one time so that the fluid passing through the housing isnot warmed by the first cell and then passed over the second cell.However, fluid could be passed over the battery cells transversely withrespect to the battery cells axes.

Turning to FIG. 2, an additional embodiment of a battery pack is shown.The battery pack 26 is like that illustrated in FIG. 1, including thehousing 34, ventilation system 38 with inlet 40 and outlet 42. Also,cells 36 are positioned within the housing. Additionally, the batterypack includes one or more baffles 46, 48, 50 and 52. The baffles directthe fluid to specific battery cells 36. Ordinarily, the fluid is passedinto channel 44 and distributed through the baffles 46 and 48.

Turning to FIG. 3, an additional embodiment of a battery pack is shown.Battery pack 60 includes a housing 62 with a venting system 64 whichenables fluid to pass around the battery cells 66. The ventilationsystem 64 includes at least one inlet 68 and at least one outlet 70.Also, the battery housing includes a fan 72. The fan 72 may include amotor 74 which may run off of the battery cells 66. Also, the fan motor74 may run off of a charging circuit when the battery pack is in acharger. The fan 72 moves fluid through the battery pack inlet. Thefluid is forced over the battery cells 66 and out the outlets 70. Thus,a positive pressure is created in the battery pack as fluid flowsthrough the battery pack as fluid flows through the battery pack 60.However, a negative pressure could be created in the battery packsucking fluid through the battery pack. The channels 73 direct the fluidthrough the battery cells so that the fluid does not continue to passfrom cell to cell but passes over different cells so that the cellsexperience the air at about the same temperature.

Also, the battery housing may include baffles 75, 76, 77, 78 like thosedescribed above.

Further, an auxiliary fan could be positioned in the tool housing itselfas illustrated in phantom in FIG. 1 to move fluid through the batteryhousing.

Temperature sensors may be positioned in the housing to monitorindividual battery cell temperature. Also, the baffles may be designedto direct fluid flow to the hottest battery cells. Thus, the cells wouldbe cooled as well as the temperature being equalized.

Turning to FIGS. 4A and 4B, an additional embodiment of the presentinvention is illustrated. Here, the battery pack includes a housing 80,and a plurality of cells 36. Also, a heat sink 84 is positioned betweenthe cells for wicking the heat from the battery cells 36. Projectingportions 86 surround the batteries to effectively move heat towards thefins 88 of the heat sink 84. Also, a plurality of slots 90 are formed inthe housing 80 to enable the heat to be removed from the battery cells36. The heat sink 84 may be of any type of metallic sink with theprojecting portion 82 either being metallic or a thermally conductivemedium, such as potting compound, gels or grease to extract the heatfrom the cells to the heat sink 84. The heat exits through the fins 88.Also, more fins, as well as larger projecting portions, surround batterycells which are known to have higher temperatures during charging of thebattery as well as discharging when the tool is used. Thus, heat isdrawn from the battery cells 36 to the heat sink. The ventilation slots90 enable fluid to pass over the fins 88 to remove heat. Also, an inlet92 may be included in the housing to enable fluid to pass from a fan inthe tool housing through the battery pack.

FIG. 4C illustrates an additional embodiment of the present invention.The battery pack is similar to that in FIGS. 4A and 4B, except thehousing 80′ does not include the plurality of slots. The plurality ofcells 36 are wrapped in a thermally conductive but electricallyinsulating substance such as tape 83 to enable heat to move from batteryto battery via a heat sink 84. The heat sink 84 is positioned betweenthe cells to wick heat from hotter battery cells and transfer the heatto battery cells having a lower temperature so that the temperatures ofthe cells are equalized within the pack. Projecting portions 86 surroundthe battery cells to effectively remove heat towards the fins of theheat sink 84. Cells which are known to have higher temperatures aredesignated with 36′. Further, the heat sink may be a metallic type likethat mentioned above, or may include thermally conductive mediums suchas potting compound, gels or grease to extract heat from hotter cellsand move it to the heat sink which, in turn, distributes the heat to theremaining cells such that the temperature within the cells is equalized.Thus, the temperature equalization of the cells enables the cells to becharged and discharged at a substantially equal rate which improves andincreases the life of the battery pack.

Turning to FIG. 5, an additional embodiment is illustrated. In FIG. 5,the battery pack includes a housing 100 surrounding a plurality of cells36. The housing 100 includes a plurality of slots 102 which act asoutlets and an inlet 104. Also, a heat pump 106 is positioned within thehousing 100. The heat pump 100 is a Peltier device, which is commonlyknown in the art. The Peltier device is coupled with heat sinks 108 and110, As the Peltier device is activated, one heat sink becomes coldwhile the other becomes hot. If the current through the Peltier deviceis reversed, the cold and hot sides reverse. Thus, the heat sinks 108,110 can be used to provide cool air into the battery housing 100 andenable the air to be baffled by baffles 112, 114, 116 and 118 to passover the battery cells 36 and exit the housing through the outlet slots.Thus, cool air would be passed into the housing to cool the batteries.In the event that the battery cells are cold, the Peltier device currentcould be reversed wherein heated fluid would be passed through thebattery pack to warm the battery cells so that they could be charged.The Peltier device is coupled to electronics 120 which may function offof the battery cells, a charger, or both, to control the cooling orheating. Also, a temperature sensor 122 may be positioned in thehousing, with respect to the battery cells, so that heating and coolingmay take place as desired.

FIG. 6 is a view like that of FIG. 5 including the heat pump 106.Additionally, a fan 124 is positioned within the housing to move thefluid through the battery pack 100. Here, fluid can be channeledthroughout the battery enabling the battery to be cooled.

Turning to FIG. 7, a battery pack is illustrated and designated with thereference numeral 130. Here, the battery pack is similar to thatillustrated in FIG. 4, however, a fan 132 is positioned within thebattery pack. The fan 132 moves fluid across the fins 88 in an attemptto expel the heat from the battery pack housing 130.

Turning to FIG. 8, an auxiliary fan module is illustrated and designatedthe reference numeral 140. The auxiliary fan module 140 includes ahousing 142 which houses a fan 144. The housing includes an inlet 146 aswell as an outlet 148. Fluid flows through the outlet 148, which issurrounded by seal 149, into the battery pack inlet 40 like thatillustrated in FIGS. 1, 2. Electrical contacts 150 are positioned withinthe housing 142 to couple with the battery electrical contacts 29 tocharge the battery cells 36. Further, electrical contacts 152 aresecured with the housing 142 to mate with electrical contacts in acharger to run the fan during charging of the battery cells. Further, anelectronic package 154 is within the housing 142 to control charging ofthe battery as well as operation of the fan 144. The electronic package154 may be coupled with the temperature sensor to operate the fan asneeded.

Turning to FIG. 9, a perspective view of a battery charger isillustrated and designated with the reference numeral 160. The charger160 includes contacts 162 to couple with a battery pack or auxiliary fanmodule to charge a battery pack. The charger 160 includes a base 164which includes the electrical contacts coupled with the base. Further avent system 166, with inlet 167 and outlet 169, is coupled with the base164 to enable air to pass into and through the battery charger and inturn the battery pack. Further, the battery charger includes anelectronics package 168 which receives the current from an AC source andconverts it into the DC source required to charge the battery pack.

The charger 160 may be utilized with the disclosed battery packs with orwithout fans in the battery pack. In the event a battery pack is usedwhich does not include a fan, convection would be used to enable airflow through the vent system 160 and in turn through the battery pack.In a situation where the battery pack includes a fan, the contacts 162would also couple with the fan electronics within the battery pack tofor operating the fan. In this event, the electronics in the chargerwould electrically couple with the fan electronics to turn on and turnoff the fan when needed.

Also, the charger could be utilized with the auxiliary fan module 140 asillustrated in FIG. 10. Here, the auxiliary fan module 140 is coupledwith the electrical contacts 162 in the charger 160 to operate the fan144 within the auxiliary fan module 140. Accordingly, the fan 144 may beturned on and off as desired.

Turning to FIG. 11, a charger 180 is shown. The charger 180 is similarto the battery charger 160 except that the battery charger 180 includesa fan 182 coupled with the venting system 166. The fan 182 moves fluidthrough an inlet 184 and forces the fluid through an outlet 186 into thebattery pack. In this type of charger 180, the fan 182 would beactivated as desired. Further, the charger electronics could be coupledwith a sensor inside of the battery pack which would be activatedthrough the electrical contacts 162. The sensor would sense thetemperature within the battery pack so that the fan could runintermittently. Also, the sensors may be removed and the fan would justrun constantly while the charger is operating.

Turning to FIG. 12, an auxiliary fan module is illustrated like that inFIG. 8. Here, the auxiliary fan module 190 includes a fan 192, an inlet194 and an outlet 196 in the housing 198. Also, a heat pump 200 asdescribed above is positioned within the housing 198. The heat pumpwould produce a cold heat sink 202 which would enable fluid to move into the housing, via the fan, and pass over the cold heat sink and intothe battery pack. The fluid would also pass over the hot side of theheat sink 206, withdrawing heat from the housing, and exhausting the airto ambient through outlet 208. In the event the battery pack is cold,the heat pump 200 may be reversed and heat may be passed into thebattery pack to warm the battery pack before charging. The fan module190 also includes electrical contacts 210 to couple with the batterypack. Also, electrical contacts 212 couple with the charger 160. Theelectronics 214 within the auxiliary fan module 190 couple with thecharger and operate the fan to move fluid into the battery pack asdesired.

Turning to FIGS. 13-15, additional embodiments of the present inventionare shown. FIG. 13 illustrates a perspective view of a batterycooler/heater device. Here, the battery cooler/heater 220 includes ahousing 222. The housing 222 includes a battery receiving portion 224.The battery receiving portion 224 may be a cutout or the like in thebattery housing 222 forming a depression to receive a battery housingpack. Further, the housing includes an inlet 226 and an outlet 228. Theinlet enables fluid to pass into a duct in the housing 222 while theoutlet enables the fluid to be passed out of the housing duct and into abattery pack. The inlet 226 is generally covered by a filter 230 and agrill 232 is attached to the housing 222 sandwiching the filter betweenthe inlet and the grill 232. The grill 232 has slots 234 to enable airto pass through the grill into the filter and turn through the inlet226.

An O-ring or some type of seal 236 is positioned around the outlet 228as shown in FIG. 14. The seal 236 mates with the battery pack toprohibit fluid from escaping around the battery pack housing while fluidis passed into the battery pack housing.

In FIG. 14, the housing 222 includes a fan 240 to move fluid between theinlet 226 and outlet 228. The fan 240 is energized and de-energized by aswitch 242. In FIG. 14, the switch 242 is a manual switch enabling theuser to manually turn on and turn off the fan 240 as desired. Also, apower cord 244 is coupled with the fan and switch electronics 246 toprovide power to the battery cooler/heater 220.

Additionally, a Peltier device 250 (illustrated in phantom) may bepositioned near the inlet which may provide cooled or heated fluid whichis drawn into the battery pack as described above. The Peltier device250 would be coupled with the electronics 246 so that the Peltier device250 may deliver cold or hot fluid flow, depending upon if cooling orheating is desired, to the battery cells.

Turning to FIG. 15, an additional embodiment of the batteryheater/cooler 220 is shown. Here, the battery cooler is like thatdescribed above, except that an automatic switch 260 has replaced themanual switch 242. Here, as the battery pack housing is slid into thebattery cooler/heater housing, the battery contacts the normally openswitch 260 energizing the fan 240. As the battery pack housing iswithdrawn from the battery cooler/heater, the switch 260 would return toits normally open position, de-energizing the fan.

Referring to FIGS. 16-18, a battery pack 300 has a housing 310, at leastone cell 318 enclosed in the housing 310 and terminals 311 connected tothe cell 318.

Preferably the housing 310 comprises two clamshell halves 310C heldtogether by screws 310S. The housing 310 may also have an upper tower310B where the terminals 311 are disposed. A cell 318 may be disposedwithin the tower 310B. Exhaust holes 315 are preferably disposed on thefront wall 310F and/or rear wall 310R of the housing 310.

Because battery pack 300 is inserted into a tool or charger by slidingthe entire pack 300 along direction X, it is preferable to provideprotrusions 312 on the side walls of the housing 310. Preferablyprotrusions 312 extend from the side walls so as to provide the userwith a grasp on the housing 310 when removing the battery pack 300 fromthe tool or charger.

Persons skilled in the art will recognize that in the present casedirection X is substantially parallel to the terminals 311 and/or thelongitudinal axis of battery pack 300. However, such persons should alsorecognize the direction X may be at an angle off the terminals 311and/or the longitudinal axis of battery pack 300.

Preferably terminals 311 are disposed on duct assembly 320. Ductassembly 320 may have walls 313 disposed between terminals 311. Inaddition, duct assembly 320 may include a duct path 321. The ductassembly 320 may also have a duct grill 321G to prevent dust, chips orother things from entering duct path 321.

Duct path 321 may be connected to a hollow plenum 340. The plenum 340preferably has opposing walls 340R and 340F. Each wall may have bosses344 contacting bosses 343 disposed on the other wall. Plenum 340 may bebuilt of one piece, or of multiple pieces assembled together.

Preferably cell 318 is disposed against plenum 340. Referring to FIGS.18 and 20, it is preferable to dispose 10 cells on both sides of plenum340. Ribs 342 may hold each cell or a group of cells in place. Internalribs 310RR may also hold each cell or a group of cells 318 in placerelative to plenum 340.

With such arrangement, air or fluid entering through the duct path 321will flow into the plenium 340. The plenium 340 preferably has holes 341for allowing the air or fluid to escape therefrom and to flow along thecells 318 towards the outlet holes 315 on housing 310.

It has been found that cells 318 closest to the center of the pack 300tend to cool slower than those cells farthest from the center of thepack 300. If the holes on the plenum 340 have the same diameter, allcells will receive the same air or fluid flow. However, by altering thesize of holes, it is possible to control the air or fluid flow alongcells 318 and thus allow more air or fluid to flow along the cellsclosest to the center of the pack, than to the cells farthest from thecenter of the pack.

Accordingly, a plenum wall may be provided with the smallest holes 343towards the periphery of the cell cluster, i.e., the group of cells.Similarly, the plenum wall may be provided with the largest holes 345 ator near the center of the cell cluster. The plenum wall may be providedwith mid-size holes 344 in between. Preferably the holes are disposedbetween two or three cells 318.

In a battery pack 300 with cells 318 which have a diameter of about 22.5mm, the diameters of holes 343, 344, and 345 would preferably be about 6mm, about 8 mm and about 12 mm, respectively. In other words, thediameters of holes 343, 344 and 345 would be about 0.267, about 0.355,and about 0.533 times the diameter of cells 318, respectively.

At the end of the cells 318 farthest away from the plenum 340, it ispreferable to provide an insulation plate 330, as shown in FIGS. 18 and21-23. Preferably, the insulation plate 330 is made of a non-conductivematerial, and it may have an adhesive material disposed on both sides ofthe plate 330.

To assist in the cooling of the cells 318, the plate 330 also have holesdisposed thereon. Preferably, these holes have different diameters.

Accordingly, the plate 330 may be provided with a center hole 332. Theplate 330 may be provided with holes 334 and 333. Holes 334 are furtherthan holes 333 from center hole 332. Accordingly, it is preferable tomake holes 334 smaller than holes 333. Preferably the holes are disposedbetween two or three cells 318.

In a battery pack 300 with cells 318 which have a diameter of about 22.5mm, center hole 332 is preferably about 12 mm wide and 25 mm long. Also,the diameters of holes 333 and 334 would preferably be about 8 mm andabout 10 mm, respectively. In other words, the diameters of holes 333,334 would be about 0.355, and about 0.444 times the diameter of cells318, respectively.

Filter 339 is preferably disposed on plate 330 to prevent dust fromand/or limit the amount of dust entering the housing 310 through holes315. Preferably filter 339 is made of a synthetic fabric mesh.

Battery pack 300 may also have a temperature indicating device 317connected to terminals 311, to indicate the temperature of cells 318.Such temperature indicating device 317 may be a thermistor, a capacitor,a thermostat, etc. The temperature indicating device 317 may be providedbetween a cell 318 and the plenum 340 (see FIG. 19), or on a cell 318 orbetween cells 318 (see FIG. 18).

If provided on a cell 318, the temperature indicating device 317 may betaped onto cell 318. The temperature indicating device 317 may becovered so that it be not exposed to the air or fluid flow.Alternatively, the temperature indicating device 317 may be leftuncovered and exposed to the air or fluid flow.

Accordingly the battery pack 300 may be manufactured as follows: aperson would take 10 cells 318 and form first and second clusters 318A,318B. Preferably, the person would wrap tape around the clusters 318A,318B to hold them together. Lead plates 316 are then connected to thedifferent cells 318.

The terminals leads 314, which are connected to terminals 311, are alsoconnected to two cells 318. Depending on the preferred embodiment, atemperature indicating device 317 may be disposed between cells 318, orattached to a cell 318 or to the plenum 340. Jumper leads 316J are thenconnected to bridge two cells of both clusters 318A, 318B. (In thismanner, both clusters will constitute a series of battery cells. Personsskilled in the art should recognize that other lead connectingarrangements may be implemented if it is preferred to dispose cells inparallel or series-parallel arrangements, etc.)

The first cluster 318A can then be disposed on one side of the plenum340. Similarly, the second cluster 318B can be disposed on the otherside of the plenum. Preferably the clusters 318A, 318B will engageplenum ribs 342.

Insulation plates 330 and filters 339 can then be disposed on theclusters 318A, 318B. The duct assembly 320 is then disposed on plenum340. The entire assembly is then disposed in the housing clamshells310C. Screws 310S are preferably used to attach both clamshells 310C.

Foam or rubber pads may be disposed on the different elements to ensurea good fit with housing 310. For example, rubber pads 338 may bedisposed on the clusters 318A, 318B, etc.

Referring to FIG. 18, a charger 400 is used for charging battery pack300. The charger 400 may have a fan 401 for moving air or fluid throughbattery pack 300. In other words, this fan 401 may blow or suck air orfluid through battery pack 300. For the sake of convenience, theembodiment disclosed herein will show air being blown from the chargerto and through the battery pack 300, but persons skilled in the art areadvised that other fluids may be moved therethrough, and/or that the airor fluid may flow from the battery pack 300 into the charger 400 or theatmosphere.

As shown in FIG. 18, fan 401 preferably moves air or fluid throughbattery pack 300 via a duct 406. Cool air may be brought in throughinlet holes 402 disposed on the charger 400. Duct 406 connects with duct321. Preferably both ducts are flushed together so that no gap existstherebetween. Furthermore, both ducts may also be axially aligned.

Fan 401 may also have an outlet 407 for blowing air through the charger400, so as to cool the charger electronic components 403. Outlet holes404 are disposed on charger 400 so as to allow warmer air to exit.

Charger 400 may also have outlet holes or vents 405. Accordingly, airexiting from the battery pack 300 may form a low pressure region abovevents 405, “pulling” air from the charger 400 outwardly. This wouldpromote air cooling of the charger electronic components 403.

FIG. 19 shows a similar charger 400′. In this charger, ducts 406 and 321are not flushed together. Instead, a chamber 406C is disposedtherebetween. Second, ducts 406 and 321 are not axially aligned.

It is known in the art to turn on the fan 401 when the battery pack 300is inserted and to turn it off completely when the charging process iscompleted or the battery pack 300 is removed. However, other fanmodulation processes are also useful.

First, it is preferable that fan 401 is turned on for a predeterminedperiod and turned off before a battery pack 300 is disposed on thecharger. This period could occur when the charger 400 is either turnedon, connected to an outlet or when a button on the charger is pushed.This would blow foreign particles, such as dust, that has settled onduct 406 and/or chamber 406C. Accordingly, such particles would not beblown into the battery pack 300 during charging. This result can also beachieved if the fan 401 is always on, on after the battery pack 300 hasbeen removed, or if the fan 401 is periodically turned on and off whenthe battery pack 300 is not disposed in the charger.

In addition, rather than fan 401 being completely turned off, it may beexpedient to just regulate the power sent to fan 401 so that fan 401rotates at a lower speed. Accordingly, fan 401 can rotate at a firstspeed before the battery pack 300 is disposed on the charger 400. Whenthe battery pack 300 is disposed on the charger 400, the fan 401 canrotate at a second speed, which is higher than the first speed. When thebattery pack 300 is then removed, the fan 401 can be turned offcompletely or brought back to a lower speed. This would also help inmaintaining the duct 406 dust-free.

Accordingly, it may be preferable to turn on fan 401 at a high firstspeed for a predetermined period and then lower the speed before abattery pack 300 is disposed on the charger. This period could occurwhen the charger 400 is either turned on, connected to an outlet or whena button on the charger is pushed.

Furthermore, the charger 400 can control the speed of fan 401 by usinginformation from the temperature indicating device 317. For example, thecharger 400 would receive information from the temperature indicatingdevice 317. If the battery pack 300 is too cold, e.g., below 20° C., thecharger 400 would lower the speed or stop fan 401. Similarly, thecharger can control fan 401 so as to maintain the temperature of batterypack 300 around a predetermined point, such as about 30° C.

In addition, charger 400 can control fan 401 so as to obtain accurateinformation from the temperature indicating device 317. For example, inan embodiment discussed above, the temperature indicating device 317 wasexposed to the air or fluid flow. Accordingly, the temperatureindicating device 317 would show a cell temperature lower than theactual cell temperature. This would render the differenttemperature-based charge termination processes useless.

Such result can be avoided if the charger 400 periodically lowers thespeed of or stops fan 401 for a predetermined period of time. This wouldallow temperature indicating device 317 to show a more accurate celltemperature, which can then be read by the charger 400 and used in itstemperature analysis. The charger 400 can then increase the speed of orstart fan 401 until the next time the charger 400 needs temperatureinformation.

Another battery pack and charger are shown in FIGS. 24-27. The teachingsof the above embodiments are incorporated herein. In the presentembodiment, battery pack 500 has a housing 501. Housing 501 containscells 502 disposed horizontally and/or substantially perpendicular tothe direction of insertion, i.e., direction Y, and/or to thelongitudinal axis of battery pack 500.

Housing 501 has holes 503 on one side. A slidable door 510 is disposednear holes 503 for sealing them. Door 510 may be disposed inside oroutside housing 501. Housing 501 may have rails 511 slidably receivingdoor 510. Door 510 may have alternating slats 510S and holes 510H.Accordingly, when door 510 is in an open position, holes 510H align withholes 503, allowing air or fluid to enter battery pack 500. When door510 is in a closed position, slats 510S align and substantially close orseal holes 503. Preferably, springs 512 connected to housing 501 biasdoor 510 towards the closed position.

When battery pack 500 is disposed on a charger 600 for charging, thebattery pack 500 is moved along the direction of insertion, causingprotrusion 602 to contact door 510 and/or door protrusion 510B. This inturn would cause door 510 to move towards the open position.

When in the open position, air blown by fans 601 will enter throughholes 503, go through holes 510H, flow along cells 502, and exit throughholes 504 disposed on the housing 501. Persons skilled in the art willrecognize that the cells 502 may be disposed on a plate 517 and held inplace by plate ribs 517R or housing ribs 501R. As before, it ispreferable to provide an insulation plate 515 and a filter 516.

In addition, persons skilled in the art should recognize that fans 601can also suck air, so that the air enters and exits the battery pack 500through holes 504 and 503, respectively.

While the above detailed description describes the preferred embodimentof the present invention, the invention is susceptible to modification,variation, and alteration without deviating from the scope and fairmeaning of the subjoined claims.

1. A battery pack to be operatively associated with an electricalappliance, said battery pack comprising: a housing having a top, abottom and a side wall portion; at least one cell disposed in thehousing; an air-flow chamber disposed in the housing proximate one endof the cell and positioned adjacent a top portion of the housing; aninlet defined by the housing, the inlet communicating with the chamberand the outside of the housing; an outlet defined by the housing, theoutlet being disposed generally opposite the inlet; a passagewayconnecting the chamber with the outlet; and a screen member disposed inthe housing.
 2. The battery pack of claim 1, wherein the inlet ispositioned adjacent the air-flow chamber.
 3. The battery pack of claim2, wherein the air-flow chamber distributes air around the cell.
 4. Thebattery pack of claim 3, wherein a channel is positioned between theair-flow chamber and the cells to direct air around the cell.
 5. Thebattery pack of claim 4, comprising a plurality of channels.
 6. Thebattery pack of claim 5, wherein a majority of the channels have auniform shape.
 7. The battery pack of claim 6, wherein the majority ofchannels are circular shaped.
 8. The battery pack of claim 5, whereinthe majority of channels have the same shape.
 9. A power tool systemcomprising: a power tool; a battery pack electrically connectable to thepower tool, said battery pack comprising a pack housing, at least onecell disposed in the pack housing, an air-flow chamber disposed in thepack housing proximate one end of the cell, an inlet defined by the packhousing, the inlet communicating with the chamber and the outside of thepack housing, an outlet defined by the pack housing, the outlet beingdisposed generally opposite the inlet, a passageway connecting thechamber with the outlet, and a screen member disposed in the packhousing; and a charger electrically connectable to the battery pack forcharging the battery pack.
 10. The system of claim 9, wherein thecharger has a charger housing, a fan disposed within the charger housingfor moving air, and a housing air outlet on the charger housing forallowing air to exit the charger housing and enter the battery packthrough the air inlet.
 11. The system of claim 9, wherein the packhousing has a top, bottom and sidewall portion.
 12. The system of claim11, wherein the air-flow chamber is positioned adjacent the top portionof the pack housing.
 13. The system of claim 12, wherein the inlet ispositioned adjacent the air-flow chamber.
 14. The system of claim 13,wherein the air-flow chamber distributes air around the cell.
 15. Thesystem of claim 14, wherein a channel is positioned between the air-flowchamber and the cells to direct air around the cell.
 16. The system ofclaim 15, comprising a plurality of channels.
 17. The system of claim16, wherein a majority of the channels have a uniform shape.
 18. Thesystem of claim 17, wherein the majority of channels are circularshaped.
 19. The system of claim 16, wherein the majority of channelshave the same shape.